Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-04-21
2001-11-06
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S275000, C528S277000, C528S279000, C528S280000, C528S285000, C528S302000, C528S308000, C528S308600, C525S437000, C524S777000, C524S783000, C524S785000, C524S788000
Reexamination Certificate
active
06313235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for preparing polypropylene terephthalate/polyethylene terephthalate copolyester (referred to as PPT/PET copolyester hereinafter), and more particularly the invention relates to a method for preparing PPT/PET copolyester by employing a process selected from between the process (a) and the process (e), whereas: process (a) involves reacting BHET, PTA and 1,3-PDO first by an esterification reaction and then by a copolymerization reaction; process (b) involves subjecting PTA and 1,3-PDO in undergoing an esterification reaction, adding BHET to the content, and then reacting the content by a copolymerization reaction; process (c) involves directly copolymerizing BHET and BHPT; process (d) involves reacting PTA, ethylene glycol (EG) and 1,3-PDO first by an esterification reaction and then by a copolymerization reaction; and process (e) involves reacting BHPT, PTA and EG first by an esterification reaction and then by a copolymerization reaction.
2. Description of the Prior Art
Generally speaking, polyethylene terephthalate (PET) is a material that has high strength and high modulus, but it is difficult to be dyed in rich colors. On the other hand, polypropylene terephthalate (PPT) is a material that can be easily dyed and has high elastic resilience, but its disadvantages are low strength and low melting point.
Therefore, many efforts have been made to improve on the dyeability of a fiber grade PET. As disclosed in U.S. Pat. No. 4,049,633 (1977), U.S. Pat. No. 4,029,637 (1977), U.S. Pat. No. 4,029,638 (1977), and U.S. Pat. No. 4,668,764 (1987), a dyeing auxiliary agent is added during the polymerization reaction to obtain a copolyester. The dyeing auxiliary agents commonly used include N,N,N′,N′-tetramethyl-1,8-diaminonaphthalene, N-(&bgr;-hydroxyethyl)-N-(3-carbomethoxybenzesulfonyl)taurine, alkali metal salt of N-benzyl-N-propyl sulfonate benzene sulfonamide, 1,4-cyclohexanedimethanol, and 2,2-bis-propane. As mentioned above, the dyeability of the copolyester can be improved by the addition of the dyeing auxiliary agent, however, the processability will be decreased such that the whole process is adversely affected. For example, not only does the commercial cationic dyeable PET in fiber form has a lower strength than conventional polyester fiber, but it also has a shorter pack life during melt spinning than conventional polyester. In addition, the cationic dyeable PET has the disadvantage of not being able to be produced in continuous mode.
Thus, researchers have thought of copolymerizing PPT and PET together to form a new polyester with improved physical properties. Ponnusamy and Balakrishnan develop a PET/PPT copolyester, which is produced by reacting dimethyl terephthalate (DMT), ethylene glycol, and 1,3-propanediol in a melt-polycondensation reaction (
J. Macromol. Sci.-Chem.,
A22 (3), pp. 373-378 (1985)). Nonetheless, methanol by-product is difficult to be recovered while DMT has always been a very expensive compound. In addition, the PET/PPT copolyester obtained through the melt-polycondensation reaction has too small a molecular weight, and the maximum intrinsic viscosity is only 0.4 dL/g with no practical value.
On the other hand, Yang Ho Park et al. develop another PET/PPT copolyester, which is produced by reacting PET oligomer and 1,3-propanediol (1,3-PDO, also abbreviated as PG) in a polycondensation reaction (
Journal of the Korean Fiber Society,
Vol. 36, No. 7, 1999). The PET oligomer (BHET) reacts only with the end residual groups of the PG compound. Therefore, theoretically, the bis-2-hydroxypropyl terephthalate (BHPT) chain obtained in the copolyester product is very limited. In addition, the reaction temperature is between 240° C. and 280° C., which exceeds the boiling point of PG. In addition, the alcohol of the PET oligomer should be reacted with 1,3-propanediol by an interchange reaction and then by the polycondensation reaction to produce the PPT/PET copolyester. The ethylene glycol by-product formed during the interchange reaction must be removed, thus the production cost is adversely increased.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above-mentioned problems and to provide a method for preparing polypropylene terephthalate/polyethylene terephthalate (PPT/PET). The present invention employs inexpensive and commercially-available starting materials such as pure terephthalic acid (PTA), ethylene glycol (EG), and 1,3-propanediol (PDO); in addition, the reaction can be performed in a conventional PET reaction device or a conventional PPT reaction device. The obtained PPT/PET copolyester has the following properties: intrinsic viscosity (IV)>0.6 dl/g, acid value (—COOH amount)<40 meq/kg, melting point=190° C.-250° C., L*>60, and b*<12. According to a preferred embodiment of the present invention, the PPT/PET copolyester has a 5 wt % to a 7.5 wt % of BHPT chain, which is suitable for use as a fiber and engineering plastic.
To achieve the object of the present invention, the method for preparing polypropylene terephthalate/polyethylene terephthalate (PPT/PET) copolyester comprises using a process selected between the process (a) and the process (e), whereas:
process (a) comprises subjecting bis-2-hydroxyethyl terephthalate (BHET), pure terephthalic acid (PTA) and 1,3-propanediol (1,3-PDO) to undergo an esterification reaction to produce BHET and bis-2-hydroxypropyl terephthalate (BHPT), and then subjecting BHET and BHPT to undergo a copolymerization reaction;
process (b) comprises subjecting PTA and 1,3-PDO to undergo an esterification reaction to produce BHPT, adding BHET, and then subjecting BHET and BHPT to undergo a copolymerization reaction;
process (c) comprises subjecting BHET and BHPT to undergo a copolymerization reaction;
process (d) comprises subjecting PTA, ethylene glycol (EG) and 1,3-PDO to undergo an esterification reaction to produce BHET and BHPT, and then subjecting BHET and BHPT to undergo a copolymerization reaction; and
process (e) comprises subjecting BHPT, PTA and EG to undergo an esterification reaction to produce BHPT and BHET, and then subjecting BHET and BHPT to undergo a copolymerization reaction.
DETAILED DESCRIPTION OF THE INVENTION
Compared with the conventional process for preparing fiber grade PET with improved dyeability, the present invention does not employ any dyeing auxiliary monomer, and the copolyester of the present invention contains PET molecular chain and PPT molecular chain which are connected to each other. In addition, conventional devices for producing polyester (such as PET or PPT) can be used in the present invention. The PPT/PET copolyester of the present invention has as good a dyeability as that of the PPT and as good physical properties as those of the PET and PPT.
Ponnusamy and Balakrishnan employ DMT as the starting material to produce PET or PPT. However, DMT itself is not accessible commercially, and the price is typically high. In addition, the methanol by-product must be removed by an additional recovering process, which inevitably increases the production cost. On the other hand, the present invention uses a pure terephthalic acid (PTA) as the starting material. Since the starting material of the present invention is more accessible, the process according to the present invention therefore is more convenient, which reduces the overall production cost.
The pure terephthalic acid (PTA) monomer used in processes (a), (b), (d) and (e) is fiber grade and preferably has the following properties: acid number=675±2, 4CBA (4-carboxybenzaldehyde)≦25 ppm, ash≦15 ppm, metal≦2 ppm, molecular weight=166.13 g/mol, and particle size≦75&mgr;.
The 1,3-propanediol used in processes (a), (b) and (d) preferably has the following properties: purity>99%, water content<2 weight %, molecular weight=76.10 g/mol, the melting point at about −32° C., and the boiling point at about 214° C. (at ambient pressure).
The ethy
Huang Jih-Chen
Kuo Tung-Ying
Shu Wen-Chuan
Tseng I-Min
Acquah Samuel A.
Industrial Technology Research Institute
Sughrue Mion Zinn Macpeak & Seas, PLLC
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